1. Field of the Invention
The present invention relates to a portable navigation device, including functionality for automatically adjusting display settings to suit various ambient lighting conditions.
2. Description of the Prior Art
Global Positioning System GPS based navigation devices are well known and are widely employed as in-car navigation devices. Reference may be made to devices that integrate a GPS receiver into a computing device programmed with a map database and that can generate navigation instructions on a display, such as the TOMTOM GO device. These portable, integrated devices are often mounted on or in the dashboard of a vehicle using a suction mount or a docking mechanism.
Reference may also be made to the Navigator series software from the present assignee, TomTom International B.V. This software, when running on a Personal Digital Assistant PDA with GPS receiver (such as a COMPAQ IPAQ) or connected to an external GPS receiver, enables a user to input to the PDA a start and destination address. The software then calculates the best route between the two end-points and displays instructions on how to navigate that route.
The term ‘navigation device’ refers to a device that enables a user to navigate to a pre-defined destination. The device may have an internal system for receiving location data, such as a GPS receiver, or may merely be connectable to a receiver that can receive location data. The device may compute a route itself, or communicate with a remote server that computes the route and provides navigation information to the device, or a hybrid device in which the device itself and a remote server both play a role in the route computation process. Portable GPS navigation devices are not permanently integrated into a vehicle but instead are devices that can readily be mounted in or docked or otherwise used inside a vehicle. Generally (but not necessarily), they are fully self-contained—i.e. include an internal GPS antenna, navigation software and maps and can hence plot and display a route to be taken.
By using the positional information derived from the integrated or external GPS receiver, the software can determine at regular intervals the position of the navigation device or PDA (typically mounted on the dashboard of a vehicle) and can display the current position of the vehicle on a map and display (and speak appropriate navigation instructions (e.g. ‘turn left in 100 m’) on the screen.
Graphics depicting the actions to be accomplished (e.g. a left arrow indicating a left turn ahead) can be displayed in a status bar and also be superimposed over the applicable junctions/turnings etc in the roads shown in the map itself. The display of the navigation device may consist of a liquid crystal display LCD for showing user location on a map and any information related to surroundings and a planned route. One example is the SAMSUNG LTE400WQ-E01 active matrix LCD module with integrated touch panel and backlight.
The set of colors for displaying a map or showing menu items on the screen of the navigation device might be pre-defined and various sets of colors might be stored as color schemes. The user may also control the backlight level of the display, which might range from full backlight level to switching off backlight completely.
One common approach is for a user to manually change the brightness settings of the display when ambient lights change, e.g. to increase brightness when using the navigation device or PDA under direct sunlight or decrease background illumination in low light situations, e.g. during the night or when driving in a tunnel. In these situations, the default brightness setting might not be appropriate because the display might be either too dark or too bright for the given lighting conditions. Lower backlight levels might also be desired for lower power consumption and an extended battery life.
It is also possible to configure a navigation device or PDA to use pre-defined color schemes for menus, maps and navigation screens. Some color schemes utilize colors with high contrast that remain visible even under direct sunlight, other color schemes are suitable for color-blind persons, and it is also known to utilize color schemes that are more suited for low light environments or when using the navigation device or PDA during the night.
However, it is not known to gradually change display brightness of a portable navigation device depending on current ambient lighting conditions and user selectable options. It is also not possible to make automatic adjustments to display brightness and/or color schemes without user interaction where and when it is most desired.
The present invention provides means for changing display settings to suit current ambient light levels and for providing user selectable preferences for automatic adjustment of display settings when ambient light levels change.